Appendix A: Fish Sea Lamprey Petromyzon marinus Federal Listing State Listing SC Global Rank State Rank S3 Regional Status Photo by John Lyons Justification (Reason for Concern in NH) Sea lampreys are blocked from much of their spawning habitat by dams. In New Hampshire they depend on functional fishways to reach suitable spawning habitat. Although Atlantic coastal populations are not currently considered threatened, there have been significant declines in lamprey populations throughout the northern hemisphere (Renaud 1997). A complex life cycle, which is dependent on multiple habitats in freshwater and marine ecosystems, makes the sea lamprey vulnerable to the effects of urbanization in coastal watersheds (Creel 2003). Sea lamprey may also be impacted by a decline in host species due to overfishing of marine fish stocks (Nislow and Kenard 2009). Distribution The sea lamprey inhabits Atlantic coastal rivers throughout eastern North America and western Europe, as far south as the western Mediterranean Sea and the gulf coast of Florida (Scott and Crossman 1973). In New Hampshire, sea lampreys migrate into the Connecticut River, Merrimack River, and coastal rivers up to the first impassable barriers. Habitat Sea lampreys spend their adult lives in the ocean as a parasite on other fish. After 20 to 30 months at sea they migrate into freshwater, following pheromones from larvae (ammocoetes) upstream (Vrieze and Sorenson 2001). Sea lampreys construct nests in gravel/cobble riffle sections of freshwater streams (Scarola 1987). Once hatched, the larvae float downstream to slow moving pools where they burrow into the substrate and filter feed on organic detritus drifting in the water column (Scarola 1987). In freshwater, sea lampreys use river reaches with gravel substrate for spawning. Spawning habitat is similar to that used by salmon, occurring at the upstream end of riffles and the tail end of pools. Ammocoetes require fine silt and sand that is loose enough to burrow into, yet protected from washing away in higher flows. These areas often occur on the inside of river bends, along stream banks, and behind structures such as boulders or fallen trees. Sea lamprey play an important ecological role in freshwater. Their nests improve spawning substrate for other fish species and create interstitial spaces between stones for macroinvertebrates (Kircheis 2004). Sea lamprey ammocoetes are filter feeders, which, in large numbers, may trap nutrients and improve water quality. Adult sea lampreys die after spawning and their carcasses release marine derived nutrients into freshwater rivers (Nislow and Kynard 2009). New Hampshire Wildlife Action Plan Appendix A Fish-132 Appendix A: Fish NH Wildlife Action Plan Habitats ● Large Warmwater Rivers ● Warmwater Rivers and Streams ● Coldwater Rivers and Streams ● Estuarine ● Marine Distribution Map Current Species and Habitat Condition in New Hampshire Sea lamprey numbers are well below their potential in New Hampshire rivers. Populations are generally declining or stable at low levels despite improvements in access to spawning habitat. Coastal Watersheds Sea lampreys typically number less than a 1,000 in coastal rivers where fish counts are recorded. The majority of sea lamprey returns are recorded each spring in the Cocheco, Exeter, and Lamprey Rivers. Sea lamprey numbers have remained low since the early 1980’s, when over 25,000 sea lampreys were removed from coastal fish ladders for medical research. Merrimack River Sea lamprey counts at the Essex dam in Lawrence average 6,603 annual returns since 1983. Counts have declined each decade, with an average of 12,220 sea lamprey counted per year between 1985 and 1994, 6,160 between 1995 and 2004, and 2,270 in the last 10 years. No sea lamprey were recorded in 2006 due to flooding. Connecticut River The average number of sea lampreys counted at the Holyoke Fishway each spring since 1975 is 34,231, with a peak of 100,000 counted in 1998. Annual sea lamprey counts at the Holyoke dam are highly variable, but returns have been below average since 2010. A recent sea lamprey pit tagging study showed that most sea lamprey move rapidly upstream between dams, but only 50% of the sea lamprey that enter fish ladders successfully pass through the ladder (Ted Castros Santos, USGS, unpublished data). New Hampshire Wildlife Action Plan Appendix A Fish-133 Appendix A: Fish Population Management Status There are no current stocking efforts focused on sea lamprey. Migrating sea lampreys are able to detect pheremones from ammocoetes, which they use to navigate to their spawning grounds. This trait makes stocking sea lamprey upstream a potential restoration strategy for seeding new populations in rivers or stream where sea lampreys have been denied access. This approach would be most effective where a migration barrier is expected to be removed or mitigated, either by dam removal or fishway construction. However, population recovery may be limited by the availability of marine host species (Nislow and Kenard 2009). Regulatory Protection (for explanations, see Appendix I) ● Harvest permit ‐ season/take regulations Quality of Habitat The extent and quality of sea lamprey spawning and juvenile rearing habitat in New Hampshire is not well known. A large proportion of historic sea lamprey spawning habitat is currently inaccessible due to impassable dams. Coastal watersheds: Access to spawning habitat for sea lamprey has improved in coastal rivers over the last 10 years. A newly constructed fish ladder at the Wiswall Dam and the removal of the Bunker Pond Dam, on the Lamprey River, has greatly increased the amount of river habitat that is accessible to Sea Lamprey (12 km). The ruins of the Wadleigh Falls Dam, in Lee, has been shown to act as a barrier to river herring migration, but its effect on sea lamprey upstream movement is unknown. Potential dam removals or fishway improvements on the Exeter, Bellamy, and Winnicut Rivers may offer opportunities for sea lampreys to increase their range in New Hampshire. In the Cocheco River, sea lampreys have access to approximately 5 km of river from the fish ladder at the Cocheco Falls Dam in Dover upstream to the Watson Dam. A possible migration barrier, known as Factory Falls, which is downstream from the Watson Dam, may limit diadromous fish passage in the Cocheco River. Merrimack River: In the Merrimack River, sea lampreys are able to reach the Hooksett Dam, although they are rarely observed at the Amoskeag Dam Fishway, in Manchester. The Souhegan River is accessible up to the McLane Dam in Milford. Baboosic Brook, a tributary to the Souhegan River, is known to contain sea lamprey spawning habitat and ammocoetes. Sea lamprey ammocoete numbers have increased at the mouth of the Souhegan River, where excellent burrowing habitat was created by sediment deposited after the Merrimack Village Dam was removed in 2008. Juveniles have also been captured in a number of other small tributaries to the Merrimack River, but the extent of spawning habitat or the total number of individuals that spawn in the mainstem is not well known. Connecticut River: Sea Lamprey ammocoetes have been documented in the Connecticut River as far north as the town of Hanover, near the mouth of the White River. The location and relative importance of sea lamprey spawning areas in the mainstem and tributaries of the upper Connecticut River is not well understood. Studies related to the relicensing of the Connecticut River dams owned by TransCanada Corporation will provide more information on sea lamprey population status and spawning habitat in the upper Connecticut River. New Hampshire Wildlife Action Plan Appendix A Fish-134 Appendix A: Fish Habitat Protection Status Habitat Management Status Efforts to improve the efficiency and monitoring of fishways will benefit sea lampreys, but dam removals will have the greatest long term benefit. The end of Atlantic salmon restoration efforts in the Merrimack and Connecticut Rivers was a setback for sea lamprey, which often share spawning areas with Atlantic salmon. Maintaining and improving fish passage solely for sea lamprey can be a challenge due to its image as a nuisance species not commonly targeted by anglers. Fisheries managers should emphasize the important ecological role of sea lamprey in freshwater and seek to improve access to spawning habitat whenever possible. Threats to this Species or Habitat in NH Threat rankings were calculated by groups of taxonomic or habitat experts using a multistep process (details in Chapter 4). Each threat was ranked for these factors: Spatial Extent, Severity, Immediacy, Certainty, and Reversibility (ability to address the threat). These combined scores produced one overall threat score. Only threats that received a “medium” or “high” score have accompanying text in this profile. Threats that have a low spatial extent, are unlikely to occur in the next ten years, or there is uncertainty in the data will be ranked lower due to these factors. Disturbance from dams that block species from spawning areas or other important habitat (Threat Rank: High) Dams block access to freshwater spawning habitat. Dams have greatly reduced the amount of freshwater habitat available to sea lamprey and other diadromous species (Limburg and Waldman 2009). Before the construction of dams on the Merrimack River, sea lamprey were documented as far north as the Baker River in the town of Wentworth (Noon 2003). Currently, the Hooksett Dam is the upstream limit of sea lamprey migration in the Merrimack River. Access to the majority of sea lamprey habitat in New Hampshire coastal rivers is currently limited by dams. Disturbance from dams that delay upstream or downstream migration (Threat Rank: Medium) Delays in migration occur at dams as fish try to successfully navigate fish passage facilities. These delays may become energetically costly to the point where they impact spawning behavior. A recent pit tagging study of migrating sea lampreys documented delays and poor passage efficiency at a number of dams on the Connecticut River (Ted Castro‐Santos, USGS, personal communication).